The lab has been focusing on exploring the circuitry and molecular mechanisms underlying memory formation and retrieval. We developed an in vivo imaging tool and data analysis system to directly measure the memory-related cortical responses in large scale. Combined with optogenetic and chemogenetic tools, we identified the memory trace neurons in layer 2 cortex and hippocampal dentate gyrus area and studied their dynamic activity of memory traces, underlying the long-term memory. Furthermore, a mechanism of epigenetic regulation was discovered within memory trace neurons to modulate the memory stability.